Antioxidants in diet may not protect against dementia, stroke after all

By Ryan Jaslow

Updated on: February 20, 2013 / 5:11 PM
/ CBS News

Antioxidants, and eating a diet filled with antioxidant-rich foods, have long been linked to disease protection like a reduced risk for dementia and stroke.

A new study, however, finds that may not be the case.

A 14-year study of more than 5,000 older adults found the amount of antioxidants a person has in their diet has no statistically significant impact in preventing against stroke and dementia.

"These results are interesting because other studies have suggested that antioxidants may help protect against stroke and dementia," study author Elizabeth Devore, an epidemiologist at Harvard Medical School and Brigham and Women's Hospital in Boston, said in a journal news release.

Antioxidants are substances that protect our cells against damaging molecules called free radicals, which are releases when the body breaks down food and environmental contaminants. Damage caused by free radicals has been linked to heart disease, cancer and other diseases, according to the National Institutes of Health.

The compounds are found in foods like blueberries, strawberries, pomegranates, tomatoes and kale. Coffee also contains antioxidants known as flavonoids.

Previous studies suggested that diets heavy in antioxidant-rich berries may prevent against memory decline, and people who eat lots of tomatoes -- which contain the antioxidant lycopene -- may be more than 50 percent less likely to have a stroke.

The new study involved 5,395 people over 55 who had no signs of dementia at the start of the study. All participants filled out questionnaires at the start of the study that contained 170 foods, marking off how often they ate them over the past year.

After 14 years, researchers found approximately 600 cases each of dementia and stroke.

Based on the amount of antioxidants in their diets, participants were split into three groups in order from lowest to highest levels, and the researchers found those with the most antioxidants in their diets were no more or less likely to develop a stroke or dementia than subjects with the lowest levels. This was confirmed through MRI brain scans. About 90 percent of the differences in antioxidant levels were attributable to the amount of coffee and tea participants drank, according to the researchers.

"It's possible that individual antioxidants, or the main foods that contribute those antioxidants -- rather than the total antioxidant level in the diet -- contribute to the lower risk of dementia and stroke found in earlier studies," concluded Devore.

A March 2012 study published in the Archives of Neurology that looked at dementia patients who took antioxidant supplements found the pills were not effective protecting against the physical markers of Alzheimer's in the brain.